The present technology relates to a microparticle measurement apparatus and a microparticle analysis method. More specifically, the present technology relates to a microparticle measurement apparatus and the like for ensuring both a sufficient fluorescence intensity from droplets discharged from an orifice and a sufficient depth of field of a droplet image.
A microparticle measurement apparatus that optically, electrically, or magnetically detects the properties of microparticles in a cell, for example, and separates and recovers only the microparticles having a predetermined property (e.g., a flow cytometer) is known.
In cell separation performed in a flow cytometer, first, a fluid stream (a laminar flow of a sample solution including cells and a sheath fluid) from an orifice formed in a flow cell is generated, the fluid stream is turned into droplets by applying vibrations on the orifice, and a charge is applied on the droplets. Further, the movement direction of the cell-containing droplets discharged from the orifice is electrically controlled in order to recover a target cell having a desired property and the other non-target cells in separate recovery vessels.
For example, as a microchip type flow cytometer, JP-A-2010-190680 discloses a “micro-particle sorting apparatus including a microchip in which a flow path through which liquid containing a microparticle flows and an orifice through which the liquid flowing through the flow path is discharged into a space outside the chip, an oscillating element configured to transform the liquid into liquid droplets and discharge the liquid droplets at the orifice, a charge mechanism for adding an electric charge to the discharged liquid droplets, an optical detection mechanism that detects an optical property of the microparticles flowing through the flow path, paired electrodes provided so as to be opposed to each other while sandwiching the moving liquid droplets therebetween along a movement direction of the liquid droplets discharged into a space outside the chip, and two or more containers that collect the liquid droplets passing between the paired electrodes”.
On the other hand, with a flow cytometer, in the illumination system, optical axis correction (calibration) for adjusting the laser light so that it is at right angles to the sample flow and is in focus is performed in order to efficiently detect scattered light and fluorescence generated from the microparticles. This calibration is performed by flowing microbeads for calibration (hereinafter, also referred to as “calibration beads”), adjusting the position and focus of a condenser lens while watching histogram data about those calibration beads, and centering the light source so that the positional relationship of the laser light, the sample flow, and the detector is optimized